How does vision work?

The eye is like a camera…

The eye functions much like a camera. Suppose you are going to take a picture of your spouse. Light rays bounce off your spouse. The image which is composed of light rays travels through the camera and is focused (brought to a point) by the lens on the camera.

If the image is in focus, the light rays strike the film producing a sharp image. If for some reason the lens is dirty, scratched, or is out of focus, the image is blurred or distorted. You then drop the film off at the store to be developed. If you have a working camera, good film and correct focus, an hour later you have a clear picture of your loved one.

How does vision work?

Suppose that you are looking at your spouse. Light bounces off your spouse and passes through the cornea (the clear front surface of the eye), through the pupil (the black circle) in the center of the iris (the colored part of the eye) and then through the lens inside your eye. The iris opens and closes to adjust the total amount of light entering the eye. The human lens, acting just like the camera lens, focuses the light onto the retina.

In young people, (under the age of 40), the human lens can adjust to add focusing power to bring near objects into better focus. The cornea contributes some of the focusing power of the eye, but it is not able to adjust like the human lens. The retina translates the light into electrical impulses which then travel to the brain via the optic nerve. The brain converts these impulses into the picture of your spouse.